Patients will be given dietary instructions and advice on exercise appropriate for the management of NAFLD (NIDDK and liverfoundation.org handouts). Patients will be prescribed 4 grams of betaine/day (2 grams PO BID) for the first 4 weeks of the study. After 4 weeks, patients in each cohort (NIDDM and non-diabetic) will be randomized (1:1) to continue receiving betaine 4 grams per day or increase to 8 grams per day for an additional 8 weeks. All patients will be seen in clinic on a monthly basis during treatment, and again 4 and 12 weeks after completion of betaine treatment. The total duration of the study is 24 weeks (12 weeks of betaine treatment and 12 weeks of follow-up).